The literature on the hematology of dairy cattle contains very important information of physiological and clinical field, but a comprehensive survey on the blood picture of Holstein cows has not been made yet in Korea. The object of the present investigation was to make good this deficiency, and to suggest standards for the blood picture of Holstein cows kept under average farming condition in this country. Observations were made on the blood picture of 30 healthy non-pregnant Holstein cows aging from 6 to 10 years. All of them were selected at random from 15 livestock farms of Deajeon area in order to determine the hematological values from January to Feburary, 1974. The ranges and mean values of erythrocyte count, hemoglobin in blood, hematocrit value, mean corpuscular volume, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, and total and differential leukocyte count were determined. The result obtained in this work were summerized as follows: 1. Ranges and mean values(with standard error) of erythrocyte count, hemoglobin in blood and hematocrit values were 4.90~7.82 and $5.83{\pm}0.12{\times}10^6/mm^3$, 7.8~10.3 and $8.7{\pm}0.11g/100ml$, and 26~38 and $30.2{\pm}0.53$ mI/100 ml, respectively. 2. Mean corpuscular hemoglobin, mean corpuscular volume, and mean corpuscular hemoglobin concentration showed ranges and mean values(with standard error) of 13.2~17.4 and $14.8{\pm}0.22$ pg, 46.0~71.8 and $52.3{\pm}0.31{\mu}m^3$, and 21.6~32.7 and $28.6{\pm}0.47$ g/100 ml, respectively. 3. Total leukocyte count showed a range of 6,300~13,600 and a mean value(with standard error) of $10,035{\pm}346/mm^3$. 4. Ranges and mean values(with standard error) of differential leukocyte counts of total neutrophil were 21~40 and $36.4{\pm}0.7%$, 1,638~4,080 and $3,233{\pm}111/mm^3$, of band neutrophil 0~9 and $3.9{\pm}0.5%$, 0~1,028 and $390{\pm}54/mm^3$, of segmented neutrophil 18~35 and $28.4{\pm}0.7%$, 1,386~3,672 and $2,842{\pm}103/mm^3$, of lymphocyte 46~69 and $55.3{\pm}1.1%$, 3,380~8,976 and $5,535{\pm}263/mm^3$, of monocyte 0~4 and $1.7{\pm}0.2%$, 0~324 and $116{\pm}21/mm^3$, of eosinophil 4~15 and $10.8{\pm}0.6%$, 540~1,725 and $1,082{\pm}72/mm^3$. No basophil was observed in this work.